In this research, mean drop size in a bench scale Kuhni column was experimentally and theoretically investigated. To measure the mean droplet size the imaging and image processing techniques were used. Two standard systems include toluene-water (high surface tension) and normal butyl acetate-water (mean surface tension) used in the experiments. Continues and dispersion phases flow rate and rotor speed are examined as variable in this study. Drop size was measured in rotor speed range 90-240 rpm and continues and dispersion phase flow rate range 18-24 lit/hr. The results showed that mean drop size was decreased with increasing rotor speed. Also the results showed that mean drop size was increased by increasing of continues and dispersion phases flow rate. The comparison of parameter effects on mean drop sized showed that continues and dispersion phases flow rate are very weaker than rotor speed.